A new class of binucleating ligands for modeling oxygen activating non heme diiron metalloenzymes, including methane monooxygenase and the R2 protein of ribonucleotide reductase, will be developed with the support of this fellowship. The target ligands are based on an easily modified naphthalene bridge that will separate two iron binding compartments and will provide two distinct advantages over current binucleating ligands: 1) the compounds will have flexibility to allow for structural changes concomitant with dioxygen binding and 2) the ligands will allow for biomimetic oxo- and hydroxo- bridges between iron ions instead of enforcing an alkoxo or phenoxo bridge that many current binuclear ligands provide. High valent diiron (IV) compounds obtained by reaction of the diiron (II) and diiron (III) complexes with dioxygen and peroxide will be examined in detail. Fundamental knowledge will be gained about the structure and reactivity of these high valent (IV) species through characterization by extended X-ray absorbance fine structure analysis, resonance Raman spectroscopy, single crystal X-ray diffraction, EPR spectroscopy, and magnetic susceptibility measurements. The ability of the high valent diiron compounds to catalyze the oxidation of hydrocarbon substrates will be examined in detail.